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高剪切式单螺杆挤压机设计,剪切,螺杆,挤压,设计
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编号无锡太湖学院毕业设计（论文）相关资料题目： 高剪切式单螺杆挤压机设计 信机 系 机械工程及自动化专业学 号： 0923202学生姓名： 沈 川 指导教师： 戴宁 （职称：副教授 ） 2013年5月25日目 录一、毕业设计（论文）开题报告二、毕业设计（论文）外文资料翻译及原文三、学生“毕业论文（论文）计划、进度、检查及落实表”四、实习鉴定表无锡太湖学院毕业设计（论文）开题报告题目： 高剪切式单螺杆挤压机设计 信机 系 机械工程及自动化 专业学 号： 0923202 学生姓名： 沈 川 指导教师： 戴宁 （职称：副教授 ） 2012年11月25日 课题来源自拟题目科学依据（包括课题的科学意义；国内外研究概况、水平和发展趋势；应用前景等）（1）课题科学意义挤压机是挤压加工技术的关键. 挤压加工技术作为一种经济实用的新型加工方法广泛应用于食品生产中, 并得到迅速发展. 挤压加工主要由一台挤压机一步完成原料的混炼、熟化、破碎、杀菌、预干燥、成型等工艺, 制成膨化、组织化产品或制成不膨化的产品. 只要简单地更换挤压模具, 便可以很方便地改变产品的造型。（2）挤压机的研究状况及其发展前景. 近十年来，挤压机行业发展迅速，CAD/CAM的电脑软件应用，数控切割机，电火花机床，加工中心等电脑控制机床的运用普遍运用于挤压模具的制造，极大满足了挤压制品的复杂程度，表面质量，尺寸精度。同时，用于冷挤和热挤的工具材料越来越多，满足了挤压工具的多样性选择。材料的热处理也越来越规范，提高了挤压工具的使用寿命。连续挤压因其连续性、投资小，见效快的优点广泛被小型企业采用。连续挤压主要运用在铝及铝合金挤压管材，简单界面的挤压制品生产。 挤压技术作为食品工业中得一项重要技术并得到更大的发展。它能将食品原料直接挤压成型得到我们需要的产品。现代食品工业用的螺杆挤压机集混合、融和、蒸煮、改性反应、 调质、组织化、成型、膨化等多种功能于一身，体现出有利于自动控制、便于灵活转产以及节能、节劳力、节省生产场地等优点。同时，挤压技术生产婴儿食品、制品的性状发生改变，产品的速溶性、冲调性提高，产品极易消化，且提高了氨基酸的含量。研究内容 高剪切式单螺杆挤压机在食品工业中的应用及工作原理 高剪切式单螺杆挤压机的总体结构 高剪切式单螺杆挤压机的主要参数计算 高剪切式单螺杆挤压机的传动系统及挤压部件设计拟采取的研究方法、技术路线、实验方案及可行性分析（1）实验方案 掌握高剪切式单螺杆挤压机的工作原理，通过对其结构及特点的研究了解挤压机的结构，从而进行对挤压部件的研究和设计。（2）研究方法 通过学习了解挤压机的结构参数，对挤压部件的参数进行计算及确定，按照挤压机的结构进行装配图及挤压部件零件图的绘制。研究计划及预期成果研究计划：2012年10月12日-2012年12月31日：按照任务书要求查阅论文相关参考资料，完成毕业设计开题报告书。2013年1月1日-2013年1月27日：学习并翻译一篇与毕业设计相关的英文材料。2013年1月28日-2013年3月3日：毕业实习。2013年3月4日-2013年3月17日：单螺杆挤压机的主要参数计算与确定。2013年3月18日-2013年4月14日：高剪切式单螺杆挤压机的总体结构设计。2013年4月15日-2013年4月28日：零件图及三维画图设计。2013年4月29日-2013年5月21日：毕业论文撰写和修改工作。预期成果：了解挤压机的工作原理,内部结构以及高剪切式单螺杆挤压机的优缺点,熟练绘制挤压机的装配图,传动系统及挤压部件的零件图。特色或创新之处 单螺杆挤压机在食品工业中操作更简单。 高剪切式单螺杆挤压机结构简单、易操作、装拆方便。已具备的条件和尚需解决的问题 设计方案思路已经非常明确，已经具备机械设计的知识。 研究问题的能力尚需加强，结构设计能力尚需加强。指导教师意见 指导教师签名：年 月 日教研室（学科组、研究所）意见 教研室主任签名： 年 月 日系意见 主管领导签名： 年 月 日英文原文Ability of a very low-cost extruder to produce instantinfant flours at a small scale in VietnamC. Mouqueta,*, B. Salvignolb, N. Van Hoanb, J. Monvoisc, S. TrechedaUR106, Nutrition, limentation Societes, IRD, BP 182, Ouagadougou 01, Burkina FasobGRET, 269 Kim Ma Street, Hanoi, Viet NamcGRET, 213 rue La Fayette, 75010 Paris, FrancedUR106, IRD, BP64501, F34 394 Montpellier cedex FranceReceived 25 July 2002; received in revised form 18 November 2002; accepted 21 November 2002Abstract Extrusion cooking is a useful process for the production of instant infant flours, as it allows gelatinisation and partial dextrinisation of starch, as well as reduction of the activity of some antinutritional factors. But existing extrusion equipment is not suited to the context of developing countries as it requires considerable financial investment and the production capacity (minimum300 kg/h) is too high. The aim of our study was to improve traditional extruders with low production capacity (about 30 kg/h) manufactured in Vietnam and to test their performance in the production of infant flours. Several blends made with rice, sesame and/or soybean have been extruded with the modified equipment that we name very low-cost extruder. In the case of blends containing soybean, starch gelatinisation was not complete, and decreased with an increase in the lipid content of the blend. The rate of trypsin inhibitor destruction evolved in a similar way. Adding water before extrusion, or extruding the blends twice was not effective in increasing the rates of starch gelatinisation or trypsin inhibitor destruction. However, the very low-cost extruder proved its ability to process the ricesesame blend that had a lipid content of less than 6 g/100 g DM, and low initial water content around 10%, wet basis (wb). In this case, extrusion led to total starch gelatinisation and the extent of starch dextrinisation, which was measured by comparing the viscosity of gruels prepared from crude and corresponding extruded blends, was sufficient to prepare gruels with substantially increased energy density. With the addition of roasted soybean flour, sugar, milk powder, vitamins and minerals, this blend could provide a nutritious instant flour usable as complementary food for infants and young children.# 2003 Elsevier Science Ltd. All rights reserved.Keywords: Extrusion cooking; Instant flour; Complementary food; Gelatinisation; Dextrinisation; Trypsin inhibitor destruction1. Introduction Extrusion cooking is one of several different processes used to produce infant flours. This particular process has many advantages that have been extensively reviewed (Bjo rck & Asp, 1983; Camire, Camire, & Krumhar, 1990; Harper & Jansen, 1985). From a nutritional point of view, extrusion cooking allows inactivation of certain antinutritional factors like trypsin inhibitor factors thus increasing protein digestibility. The high temperature generated during processing ensures satisfactory hygienic quality, and in general results in starch gelatinisation, thus leading to an instant flour. If not truly instant, the flour is at least pre-cooked, and the subsequent time required to cook the gruel is considerably reduced. During extrusion cooking, raw materials also undergo high shear, thus allowing partial starch hydrolysis (Colonna, Doublier, Melcion, De Monredon, & Mercier, 1984). The extent of hydrolysis determines the energy density at which it will be possible to prepare a gruel of semi-liquid consistency that is acceptable to infants. At a given consistency, the more important the starch is hydrolyzed, the higher the gruel energy densitywill be. In spite of these advantages, the adoption of extrusion cooking processing for the production of infant flour in developing countries is still limited. Only a few industrial units produce extruded flour at a large scale mainly in response to the need of international or non-govern- 0308-8146/03/$ - see front matter # 2003 Elsevier Science Ltd. All rights reserved. doi:10.1016/S0308-8146(02)00545-9 Food Chemistry 82 (2003) 249255 /locate/foodchem *Tel.: +226-30-67-37; fax: +226-31-03-85. E-mail address: claire.mouquetird.bf (C. Mouquet). mental organisations for emergency supplies. The main reason for this is that most extruders are designed for large-scale production, thus requiring very high investment and technical knowledge. Even the so-called low-cost extruders, or dry extruders that were developed for the production of complementary foods at the beginning of the 1980s by the university of Colorado (Harper, 1995; Harper & Jansen, 1985; Said, 2000), are too costly and their production capacity is too high (about 55,000 dollars for a machine with a production capacity of 1 ton per hour), and are thus not affordable for developing countries. The development of a small simple machine, with a small production capacity (about 30 kg/h) is therefore of great potential interest. The Vietnamese context is particularly well suited for the development of the production of infant flour by extrusion cooking for several reasons. 1. In rural areas and particularly in the plains, mothers prepare a thermos of boiled hot water each morning in order to have a supply of safe drinking water available during the day, and this water could easily be used for the preparation of a gruel with an instant flour 2. A rudimentary extrusion cooking process has been used for many years in the countryside; simple extruders with very small production capacity already exist and are used for the production of snacks or cassava noodles sold in the street. These machines were probably originally designed in the United States at the end of the nineteenth century for the extrusion of plastic. 3. These small extruders are now manufactured locally in small mechanical workshops, and it is also easy and cheap to construct spare parts locally for the maintenance of the machines. Occasional attempts have been made to produce instant infant flours using these rudimentary localextruders but these efforts have not continued, firstly because their impact on nutritional quality of infant flours was not satisfactory, and secondly because the machines were not sturdy and often broke down during production. Taking the features of this specific context into account, we modified the rudimentary type of local extruder to improve their ability to produce infant flour, as well as their sturdiness. These improved extruders with limited production capacity were named very low-cost extruders in reference to the low-cost extruders that Harper and Jansen already developed for the production of nutritious precooked foods for developing countries (Harper &Jansen,1985). The objective of this study was to test the performance of these improved very low-cost extruders and, in particular, to evaluate the instant character of the flour, the extent of starch dextrinisation and the residual trypsin inhibitor activity of extruded blends.2. Materials and methods 2.1. Extrusion cooking equipment The very low-cost extruder we used is a simple single- screw autogenous extruder manufactured in Vietnam by a small enterprise named Mechanical Workshop no. 14700, (Phan Chu Trinh Street, Da nang City) according plans that we furnished (see photo in Fig. 1). The drive motor has a power of 10.5 kW. The barrel length is 200 mm with a length/diameter ratio of 5 and has a central cylindrical die of 5 mm in diameter and 9 mm in length. The rotating speed of the screw is high (500 rpm), thus allowing high shear. The design of the screw was modified (constant pitch and gradual decrease in the flight depth), to allow a progressive increase in friction forces and consequently in the temperature inside the barrel. The screw diameter is 40 mm and the root diameter increases gradually from 33 to 38 mm (see photo in Fig. 2) The extruder barrel wall has reverse helical grooves to enhance forward conveyance of the product. To ensure a regular feeding rate, the extruder is equipped with a motorised feeding screw that allows feeding rates from 5 to 39 kg/h. Residence time is between 4 and 20 s, which is very short in comparison to other extruders but longer than the residence time observed in rudimentary Vietnamese extruders.2.2. Raw materials The raw materials used to prepare composite flours were the cheapest and the most easily available on the Vietnamese market. The basic cereal was polished rice. Soybean and sesame were added to increase lipid and protein contents. All raw materials were bought locally. Soybean was dried in an oven to reach a dry matter content above 92%, wet basis (wb), before being dehulled in an abrasive disk huller equipped with a cyclone to remove hulls and straws. After dehulling, the abrasive disks were brought closer and the soybean passed a second time in the machine to be roughly ground to a size of about 2 mm. Different infant flour formulas (flours A, B, C and D) were calculated to achieve the minimum protein and lipid contents of respectively, 12 and 8 g/100 g DM required for complementary foods, after addition of a premix to the extruded blends (Table 1). The premixC. Mouquet et al. / Food Chemistry 82 (2003) 249255Fig. 1. The very low-cost extrusion-cooker used for experiments (designed and manufactured in Vietnam). 1. Feeding hopper; 2. screw and barrel;3. central cylindrical die; 4. control panel (amperage, temperature, feeding screw On/Off, extruder On/Off); 5. feeding screw speed variator.Fig. 2. Main spare parts of the very low-cost extrusion-cooker. 1. Barrel; 2. screw with gradual decrease in the flight depth and constant pitch; 3. cylindrical die of 5 mm in diameter and 9 mm in length.Table 1Formulas and calculated protein and lipid contents of final composite floursComposition (g/100 g dry matter) Nutrient content of final flour (g/100 g DM) Ingredients blended Ingredients added Lipid Protein before extrusion after extrusion Rice Soybean Sesame Roasted soybean Premix Flour A 49.9 21.7 5.7 0.0 22.7 10.03 15.45 Flour B 50.2 27.1 0.0 0.0 22.7 8.05 16.63 Flour C 50.2 24.7 2.3 0.0 22.7 8.82 16.70 Flour D 52.4 0.0 4.9 20.0 22.7 10.12 16.33 Calculated from Souci et al. (2000).Premix prepared by blending sugar (66%), milk powder (22%), salt (4%), vitamins and minerals (7%) and vanilla aroma (1%).Total N content multiplied by 5.80, 5.30, 5.71 and 6.38 for rice, soybean, sesame and milk powder, respectively. (sugar 66%, milk powder 22%, salt 4%, aroma 1%, vitamins and minerals 7%, wt.) was added in order to meet recommendations for vitamin and mineral contents and confer suitable organoleptic characteristics to the flours. For blend D, the formula was calculated taking into account the addition of roasted soybean flour bought on the local market after extrusion to achieve requiredprotein and lipid contents. The formula calculations were made with data from food composition tables (Souci, Fachman, & Kraut, 2000). Extrusion cooking experiments were performed on rice alone and on the different blends of rice, soybean and/or sesame used for the preparation of flours A, B, C and D (Table 2). After extrusion, all extrudates were ground (particle size 500 mm) before biochemical analysis.C. Mouquet et al. / Food Chemistry 82 (2003) 249255Table 2Composition and calculated lipid and protein contents of rice and blends before extrusion Composition (g/100 g DM) Nutrient contenta (g/100 g DM) Rice Soybean Sesame Lipid Proteinb Rice 100.0 0.0 0.0 0.71 7.84 Blend A 64.5 8.1 7.4 11.18 18.25 Blend B 65.0 35.0 0.0 8.61 19.78 Blend C 65.0 32.0 3.0 9.60 19.09 Blend D 91.4 0.0 8.6 5.47 8.82 Calculated from Souci et al. (2000). Total N content multiplied by 5.80, 5.30 and 5.71 for rice, soybean and sesame, respectively.2.3. Starch gelatinisation rate Total starch content of composite flours was determined by the enzymatic method of Batey (1982). Analyses were made in duplicate and both values are given. The extent of starch gelatinisation during extrusion cooking was determined in duplicate by a method based on the evaluation of amyloglucosidase hydrolysis susceptibility (Chiang & Johnson, 1977; Kainuma, Matsunaga, Itagawa, & Kobayashi, 1981). The gelatinisation rate is the ratio of starch fraction susceptible to amyloglucosidase hydrolysis and total starch (minimum, maximum and mean values are given).2.4. Preparation of gruels Crude and extruded blend were ground and the flours obtained were used for the preparation of gruels with different dry matter contents using: 1. A cooking procedure comprising mixing flour with cold demineralised water into a slurry and cooking on a hot plate (300 C) with continuous stirring for 5 min once the mixture started to boil.2. An instant procedure comprising adding demineralised water heated to 75 C to the flourand stirring vigorously. After preparation, gruels were allowed to cool to 45 C before viscosity measurements. Dry matter contents of the gruels were determined by oven drying at 105 C to constant weight.2.5. Apparent viscosity measurements Apparent viscosity measurements were performed on gruels with a Haake viscometer VT550 with SV-DIN coaxial cylinders driven by a PC computer with the Rheowin 2.67 software. We applied the measurement procedure proposed by Mouquet and Treche (2001), i.e. shear rate of 83 s1, shear time of 10 min and measurement temperature of 45.00.5 C.2.6. Procedure used to check the instant character of extruded blends To our knowledge, the term instant, which usually describes dehydrated precooked food usable after the simple addition of hot water, is not accurately defined from a biochemical point of view. As starch becomes easier to digest when it is completely gelatinised and swollen, we chose to evaluate the instant character by comparing apparent viscosity of gruels prepared by the instant and the cooking procedures with the same dry matter content. Two scenarios can be expected: if the apparent viscosity of the gruel prepared with the instant procedure is equal or slightly higher than the viscosity of the gruel prepared with the cooking procedure, then the flour can be considered as instant. If it is lower, it implies that part of the flour starch is not totally precooked during the extrusion cooking stage and will continue to swell during the cooking of the gruel, thus leading to an increase in viscosity.2.7. Trypsin inhibitor activity Trypsin inhibitor activity (TIA) was determined induplicate by the method of Kakade, Rackis, MacGhee, and Puski (1974), modified by Smith, Van Megen, Twaalfhoven, and Hitchcock (1980), and both values, expressed in trypsin inhibitor units (TIU) per 100 g DM, are given. The percentage of trypsin inhibitor destroyed during extrusion cooking were calculated from the ratio between TIA before and after extrusion, and mean, minimum and maximum values are given.3. Results and discussion3.1. Effect of very low-cost extruder on starch gelatinisation rate The main characteristics of the different extruded blends are given in Table 3. In all cases, we observed an increase in dry matter content after extrusion cooking. This increase is due to water loss by instant vaporisation at the exit of the die. For extruded rice and blend D only, the gelatinisation rate exceeded 90%, from which we estimated that gelatinisation rate had reached a satisfactory level. For extruded blends A, B and C, the gelatinisation rate after extrusion cooking ranged from 56 to 83%. The remaining native and, thus, non-digestible starch content was non negligible, and we consequently considered that the corresponding flours could not be used as instant flours, even though they appeared to be precooked.C. Mouquet et al. / Food Chemistry 82 (2003) 249255Table 3Effects of processing with the very low-cost extruder on the starch gelatinisation rate and the trypsin inhibitor activity of rice and different blendsBlend used for Dry matter Total starch Gelatinised Gelatinisation Trypsin inhibitor activity TI destroyed TIdestroyed (%) extrusion cooking content content starch content rate(%)c (g/100g, wb) (g/100g DM) (g/100g DM) TIU/g DM TIU/g DM of soybean Rice Before ECa 86.0 91.993.9 10.811.5 12 (1112) eRice After EC 90.5 85.087.8 93 (9196)A Before EC 88.9 55.557.3 9.410.9 18 (1620) 12,21312,246 44,25044,490eA After EC 90.4 30.333.3 57 (5360) 57666091 20,89022,066 52 (5053)B Before EC 90.1 61.265.9 10.612.7 18 (1621) 13,51813,900 37,65538,719eB After EC 95.5 51.153.8 83 (7887) 31403491 95489924 76 (7478)C Before EC 90.6 56.358.5 10.511.3 19 (1820) 13,39413,774 40,83641,994eC After EC 95.4 44.046.6 79 (7583) 23802574 67778327 82 (8183)eC After EC 89.9 35.639.0 65 (6169) 60416625 18,41820,198 53 (5156)eC After EC 92.0 45.846.0 80 (7882) 19722112 60146438 85 (8486)eC After EC 90.8 44.344.4 77 (7679) 21672292 66086990 84 (8384)D Before EC 88.7 84.486.3 19.321.7 24 (2325) eD After EC 92.7 82.384.9 98 (95100) wb, wet basis; DM, dry matter; TIU, trypsin inhibitor units; TI, trypsin inhibitor; EC, extrusion cooking; eRice, extruded rice; eA, extruded blend A,. . .Analyses were made in duplicate and both values are given. For ratios, mean values calculated from analyses results are given (minimum and maximum values in parentheses). eCa, the blend C was added with water (10ml/100g) before extrusion cooking, lowering the initial dry matter content of the blend to 81.8 g/100 g DM. eCb, the blend B was extruded a first time, then sesame and water (10 ml/100 g, wb) were added and the blend extruded a second time. eCc, the blend C was extruded twice, with addition of water (15 ml/100 g, wb) between the two treatments. To check this, the apparent viscosity of gruels prepared at different concentrations with the flours obtained from extruded blends according to the two different procedures (instant and cooking) were compared. The viscous behaviour of gruels prepared with the flour of the crude blend was also determined. Results obtained with rice, and with blends A and D are presented in Fig. 3. The curves of apparent viscosity of gruels obtained with the flour of the extruded blend D (Fig. 3c) were almost superimposed for the two gruel preparation procedures indicating that this procedure had no major effect on its consistency. This confirms that flour D can be sold and used as instant flour. However, in the case of the flour of the extruded blend A (Fig. 3b), the viscositycurve of gruels prepared by the instant procedure was very far from those of gruels prepared by boiling for 5 min, indicating that a starch fraction that had not gelatinised during the extrusion cooking treatment, gelatinised and swelled during gruel preparation, leading to a much more viscous gruel at the same concentration. The viscous behaviour of those gruels was very close to that of gruels prepared with the corresponding flour of crude blend and we concluded that the extrusion cooking treatment had had very little effect on starch in this case. In the case of the extruded rice flour (Fig. 3a) surprisingly, gruels cooked by boiling for 5 min were thinner at the same concentration, than those prepared by the addition of hot water. This can be explained by a partial solubilisation of swollen granules of starch during the cooking of the gruel that resulted in reduced viscosity. Thus, while extruded rice or blend D resulted in flours that can be considered instant, the persistence of a non gelatinised fraction of starch in blend A after extrusion cooking led us to conclude that the processing with very low-cost extruders was not appropriate for this blend.3.2. Effect of very low-cost extruder on starch dextrinisation The results presented in Fig. 3 can also be used to evaluate the intensity of starch dextrinisation during the extrusion cooking process. Partial starch dextrinisation is desirable because it reduces swelling during gruel preparation, thus allowing an appropriate semi-fluid consistency to be maintained at a higher concentration, i.e. higher energy density. To achieve this, we measured the gain in dry matter content between gruels prepared at the same apparent viscosity with crude flours according to the cooking procedure and with flours of extruded blends according to the instant procedure when starch gelatinisation was complete (extruded rice and blend D), or according to the cooking procedure when starch gelatinisation was only partial (extruded blend A). At the apparent viscosity value of 1.5 Pa.s, which corresponds to a thick but spoonable gruel(Mouquet & Treche, 2001), the increases in dry matter content of gruels due to the extrusion cooking treatment for rice and blend D were 5.7 and 4.3 g/100 g of gruel, respectively (Fig. 3a and c). This increase was limited to 1.2 g/100 g of gruel for extruded blend A, demonstrat-ing once again the less drastic effect of the extrusion cooking treatment (Fig. 3b).C. Mouquet et al. / Food Chemistry 82 (2003) 249255Fig. 3. Effect of the concentration on the apparent viscosity of gruels prepared with rice and experimental blends according to different procedures. + Crude flour, boiling 5 min; extruded flour, addition of water at 75 C; extruded flour, boiling 5 min.Fig. 4. Influence of the initial lipid content of the blend on the percentages of trypsin inhibitor destruction and starch gelatinisation during processing in very low-cost extruder (mean, minimum and maximum values).3.3. Effect of very low-cost extruder on the reduction of trypsin inhibitor activity The TIA of crude grains of soybean bought on the local market is very high, about 40,000 TIU/g DM of soybean (Table 3). After extrusion cooking, we observed a reduction in TIA that took place in a similar way to the gelatinisation rate as a function of the composition of the blend (Fig. 4). The lipid content of the blends seemed to be one of the main factors affecting the severity of the extrusion cooking treatment. It is indeed well known that lipids, by lubricating the screw and the internal surface of the barrel, decrease friction forces and thus reduce the maximum temperature inside the extruder. In our experiments, until it reached 6 g/100 g DM, the lipid content of the blends appeared to have no effect on starch gelatinisation. Beyond this value, the starch gelatinisation rate started to decrease, resulting in reduced efficiency of the extrusion cooking treatment. We also observed a simultaneous decrease in trypsin inhibitor destruction rates, as lipid content increased. These results are consistent with the threshold value of 7 g/100 g DM previously mentioned for lipid content under which it becomes difficult to transform mechanical energy into heat with a single-screw extruder and without steam injection (Huber, 2000). To increase the efficiency of the extrusion cooking process, we tried several combinations of treatment: 1. We increased the initial water content of blend C (trial Ca) from 9.5 to 18.2 by water spraying to favour starch gelatinisation assuming that the gelatinisation temperature decreases with increasing initial water content of the blend (Lelievre, 1973), 2. We attempted to amplify the effects of extrusion cooking by repeating the treatment: in trial Cb, we first extruded blend B (rice and soybean) and then added sesame to obtain blend C for the second extrusion. In trial Cc, we twice extruded the complete blend C (rice, soybean and sesame). We had to add water to the blends between the two extrusion cooking treatments, because after the first extrusion cooking treatment, the dry matter content was more than 95%, and there was a risk of damage to the extruder. The quantity of water added was calculated to reachan initial dry matter content of about 90%, close to the values of initial blends. The effects of these combined or modified treatments on starch gelatinisation and trypsin inhibitor destruction rates are given in Table 3. The results of trial Ca show that the addition of water to the initial blend had a strong negative effect on the efficiency of the extrusion cooking treatment probably due to a marked decrease in the maximum temperature reached inside the barrel (maximum temperature measuredon the external side of the barrel near the die was 156 C without water addition, and decreased to 108 C when water was added before extrusion). The percentages of gelatinised starch and destroyed trypsin inhibitor fell from 79 and 82% respectively, without the addition of water, to 65 and 53%. The very low-cost extruder is not equipped with a steam injection system to balance the reduction of the friction forces due to the smoothing effect of the water. For trials Cb and Cc,the second extrusion cooking treatment had no beneficial effects on the gelatinisation rate and allowed an increase of only a few percent in the trypsin inhibitor destruction rate, which was not sufficient to justify performing the second extrusion cooking operation in commercial production.4. Conclusion The results of our experiments showed that the kind of very low-cost extruders with a small production capacity that we improved in Vietnam is suitable to process blends with low water content (around 10%, wb) and low lipid content (below 6%, db). In these conditions, the ricesesame blend extruded with this equipment resulted in total starch gelatinisation, which is required if the flour is to be sold as instant flour. Starch was also partially dextrinised during the treatment, thus allowing the preparation of gruels of higher energy density. After extrusion, the addition of roasted soybean flour and premix allowed the appropriate macro and micronutrient balance required for a complete infant flour to be achieved.ReferencesBatey, I. L. (1982). Starch analysis using thermostable a-amylase. Starch, 4, 125128.Bjo rck, I., & Asp, N. (1983). The effects of extrusion cooking on nutritional valuea literature review. Journal of Food Engineering, 2, 281308.Camire, M., Camire, A., & Krumhar, K. (1990). Chemical and nutritional changes in foods during extrusion. Critical Reviews in Food Science and Nutrition, 29(1), 3556.Chiang, C. J., & Johnson, J. A. (1977). Measurement of total and gelatinized starch by glucoamylase and o-toluidine reagent. Cereal Chemistry, 54(3), 429435.Colonna, P., Doublier, J. L., Melcion, J. P., De Monredon, F., & Mercier, C. (1984). Extrusion cooking and drum drying of wheat starch. I. Physical and macromolecular modifications. Cereal Chemistry, 61(6), 538544.Harper, J. (1995). Low-cost extrusion: possibilities for Africa. The South-African Journal of Food Science and Nutrition, 7, 142147.Harper, J., & Jansen, G. (1985). Production of nutritious precooked foods in developing countries by low-cost extrusion technology. Food Reviews International, 1(1), 2797.Huber, G. R. (2000). Twin-screw extruders. In M. N. Riaz (Ed.), Extruders in food applications (pp. 81114). Texas: Technomic publishing Co.Kainuma, K., Matsunaga, F., Itagawa, M., & Kobayashi, S. (1981). New enzyme system b-amylasepullulanase to determine the degree of gelatinization and retrogradation of starch or starch products. Journal of Japanese Society on Starch Science, 28(4), 235240.Kakade, M. L., Rackis, J. J., MacGhee, J. E., & Puski, G. (1974). Determination of trypsin inhibitor activity of soy products: a collaborative analysis of an improved procedure. Cereal Chemistry, 51, 376382.Lelievre, J. (1973). Starch gelatinization. Journal of Applied Polymer Science, 18, 293296.Mouquet, C., & Treche, S. (2001). Viscosity of gruels for infants: a comparison of measurement procedures. International Journal of Food Sciences and Nutrition, 52, 389400.Said, N. W. (2000). Dry extruders. In M. N. Riaz (Ed.), Extruders in food applications (pp. 5162). Texas: Technomic publishing Co.Smith, C., Van-Megen, W., Twaalfhoven, L., & Hitchcock, C. (1980). The determination of trypsin inhibitor levels in foodstuffs. Journal of the Science of Food and Agriculture, 31, 341350.Souci, S., Fachman, W., & Kraut, H. (2000). Food composition and nutrition tables (6th ed). London: Medpharm Scientific Publisher &CRC Press.中文译文越南小规模婴儿粉“低成本挤压机”的生产效能C. Mouqueta,*, B. Salvignolb, N. Van Hoanb, J. Monvoisc, S. TrechedaUR106, Nutrition, limentation Societes, IRD, BP 182, Ouagadougou 01, Burkina FasobGRET, 269 Kim Ma Street, Hanoi, VietNamcGRET, 213 rue La Fayette, 75010 Paris, FrancedUR106, IRD, BP64501, F34 394 Montpellier cedex France2002年7月25日：初稿 2002年11月8日：校稿 2002年11月21日：发布摘要 挤压蒸煮是一种生产即时婴儿米粉有效的方法，因为它可使淀粉糊化和部分糊精化，并且使一些抗营养因子的活性降低。但是，现有的挤出设备不适合于发展中国家，因为它需要大量的财政投资，并且生产能力（最小范围内300公斤/小时）过高。我们研究的目的在于改善越南传统挤出机生产能力低（约30公斤/小时）的问题，以及测试其在生产婴儿粉时的效能。我们把这种可以混合大米、芝麻和/或大豆挤压的设备叫做“低成本挤压机”。在混合物中含大豆的情况下，淀粉不能完全糊化，并且糊化程度还随着混合物中脂肪含量的增加而减少。胰蛋酶抑制剂的破坏率以类似的方式发展。挤压前加入水，或挤压两次不能有效的提高淀粉的糊化率或胰蛋白酶抑制剂的破坏率。然而，事实证明“低成本挤压机”能够处理低初始含水量10左右，湿基（wb），脂肪含量少于6g/100gDM。在这种情况下，挤压会导致淀粉的整体糊化和淀粉的糊精化程度加深。通过测量挤压前准备稀糊化混合物与挤压后混合物的粘滞度的对比，就可以知道稀糊化所需要的能量密度。随着烤熟的大豆粉、奶粉、维生素以及矿物质的加入，这种混合物所含有的营养可以在婴幼儿辅助食品中使用。 #2003 Elsevier科学有限公司保留所有权利。 关键词：挤压蒸煮，即时面粉;补充食品，糊化;糊精化;胰蛋白酶抑制破坏剂。1 引言 挤压蒸煮是婴儿米粉生产的几个不同过程之一。这种特殊的过程拥因有许多优势而被广泛采用。 (Bjo rck & Asp, 1983; Camire, Camire, &Krumhar, 1990; Harper & Jansen, 1985).从营养角度上来说，挤压蒸煮可以灭活某些抗营养因子如胰蛋白酶，而这可以增加蛋白质的消化率。挤压过程中的高温环境，可以保证卫生要求，并使得淀粉基本糊化，从而生产出速溶粉。如果没能真正的速溶化，但此时，混合物已经预热，可以大大减少其稀糊化所需时间。挤压蒸煮过程中，原料还经过高剪切过程，从而使淀粉部分降解。(Colonna, Doublier, Melcion, De
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